Dynamics of Liquid Lithium Atoms: Time Scales and Dynamic Correlation Functions

Based on the configuration data on molecular dynamics simulation of the lithium melt near the melting point, the memory functions of the relaxation process of the density fluctuations are calculated. It is established that for the range of wave numbers corresponding to microscopic spatial scales, the memory functions of the first four orders are characterized by oscillating behavior. This feature indicates that the model memory functions in the case of phenomenological description of the dynamics of the density fluctuations can not have the form of monotonically decreasing functions. The frequency characteristics of the dynamic structure factor for a wide range of wave numbers are calculated. The convergence of the relaxation parameters Δ4(k) and Δ5(k) for the range of wave numbers from the hydrodynamic regime (k → 0) to the values of k is higher than the boundary of the first pseudo-Brillouin zone (for k ≈ 0.87km) are detected. The characteristic time scales of the process of structural relaxation of the density fluctuations are determined.